1. Field of the Invention
The present invention relates generally to four-cycle internal combustion engines, and more specifically, to an internal combustion engine with a variable length connecting rod that increases the length of the power and exhaust strokes relative to the intake and compression strokes.
2. Description of the Related Art
A four-cycle internal combustion engine has four strokes: the intake stroke, during which the intake valve opens and the piston travels downward away from the cylinder head, thereby allowing the fuel/air mixture to enter the cylinder; the compression stroke, during which the intake valve closes and the piston travels back toward the cylinder head, thereby compressing the fuel/air mixture that entered the cylinder during the intake stroke; the power stroke, during which the fuel/air mixture in the cylinder is ignited, thereby forming high-pressure gases that force the piston down the cylinder; and the exhaust stroke, during which the exhaust valve opens and the piston moves back toward the cylinder head, thereby causing the high-pressure gases that were formed during the power stroke to be emitted as exhaust. The power generated during the power stroke is what drives the engine.
In current four-cycle internal combustion engines, the distance traveled by the piston during the intake and compression cycles is the same as the distance traveled by the piston during the power and exhaust cycles. In other words, the volume of all four cycles is equal. The distance traveled is sometimes referred to in terms of a ratio, in this case, the ratio of the distance of the piston from the cylinder head when it is at the end of the intake (or power) stroke and the beginning of the compression (or exhaust) stroke to the distance of the piston to the cylinder head at the beginning of the intake (or power) stroke and the end of the compression (or exhaust) stroke. This ratio is referred to as the “compression ratio,” which is typically 8:1 for a four-cycle internal combustion engine that uses gasoline.
The theoretical efficiency of this type of engine is a function of the compression ratio. An 8:1 compression ratio corresponds to a thermodynamic efficiency rate of approximately 56%. If the engine cycle is altered so that the volume of the power and exhaust cycles is greater than the volume of the intake and compression cycles, then the thermodynamic efficiency rate of the engine increases. For example, the theoretical efficiency of an engine with an 8:1 compression ratio and a 16:1 power ratio is 67%, which represents a 20% increase in efficiency over an engine in which the volume of the intake/compression strokes is equal to the volume of the power/exhaust strokes. Assuming this increase in thermodynamic efficiency translates into a corresponding increase in mechanical efficiency, this would result in an increase in gas mileage from 25 miles per gallon to 30 miles per gallon for the average vehicle.
Accordingly, it is an object of the present invention to provide a design for four-cycle engines (four-cylinder or six-cylinder) that will increase the volume of the power and exhaust strokes relative to the intake and compression strokes and that can be used with any available fuel, including gasoline, diesel fuel and ethanol. It is a further object of the present invention to provide a redesigned engine that requires no changes to existing valves or timing. Yet another object of the present invention is to decrease the temperature and pressure of the exhaust gases, thereby increasing fuel efficiency by capturing more of the energy from the combustion of the fuel.